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                  <h1>每天学习一个shell技能（8）</h1>
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                        	<h2 id="toc_0">shell 终端打印</h2>

<pre><code class="language-text">```
printf &quot;%-5s %-10s %-4s \n&quot; NO Name Mark
printf &quot;%-5s %-10s %-4s \n&quot; 1 kael 100
printf &quot;%-5s %-10s %-4s \n&quot; 2 linda 99
printf &quot;%-5s %-10s %-4s \n&quot; 3 rouse 98

// 打印结果
NO    Name       Mark 
1     kael       100  
2     linda      99   
3     rouse      98  
```
</code></pre>

<blockquote>
<p>printf 行尾 默认自带换行 \n</p>
</blockquote>

<ul>
<li>%-5s : 左对齐，宽度为5的字符串替换；默认右对齐</li>
<li>%-4.2f:指定保留2位小数</li>
</ul>

                        
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                    <span class="date">2018/4/9</span>
                    <span>posted in&nbsp;</span> 
          				  
          					    <span class="posted-in"><a href='shell.html'>shell</a></span>
          				   
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                  <h1>每天学习一个shell技能（7）</h1>
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                        	<h2 id="toc_0">文件包含 导入文件</h2>

<p>测试文件  test1.sh</p>

<pre><code class="language-text">#!/bin/bash
# author:菜鸟教程
# url:www.runoob.com

url=&quot;http://www.runoob.com&quot;
</code></pre>

<p>测试文件 test2.sh</p>

<pre><code class="language-text">#!/bin/bash
# author:菜鸟教程
# url:www.runoob.com

#使用 . 号来引用test1.sh 文件
. ./test1.sh

# 或者使用以下包含文件代码
# source ./test1.sh

echo &quot;菜鸟教程官网地址：$url&quot;
</code></pre>


                        
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                   <a href="15226648731246.html">Read more</a>&nbsp;&nbsp; 
                    <span class="date">2018/4/2</span>
                    <span>posted in&nbsp;</span> 
          				  
          					    <span class="posted-in"><a href='shell.html'>shell</a></span>
          				   
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                  <h1>每天学习一个shell技能（6）</h1>
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                        	<h2 id="toc_0">test</h2>

<h3 id="toc_1">test文件</h3>

<pre><code class="language-text">if test -e ./test.sh
then
    echo &#39;文件已存在!&#39;
else
    echo &#39;文件不存在!&#39;
fi
</code></pre>

<ul>
<li>-e fileName ： 如果文件存在则为真</li>
<li>-r  fileName : 如果文件存在且可读则为真</li>
<li>-w fileName : 如果文件存在且可写则为真</li>
<li>-x fileName : 如果文件存在且可执行则为真</li>
<li>-s fileName: 文件存在且至少有一个字符</li>
<li>-d fileName : 文件存在且为目录</li>
<li>-f fileName: 文件存在且为文件</li>
<li>-c fileName:文件存在，且为字符型特殊文件</li>
<li>-b fileName: 如果文件存在且为块特殊文件则为真</li>
</ul>


                        
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                    <span class="date">2018/4/2</span>
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                  <h1>每天学习一个shell技能（5）</h1>
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                        	<h2 id="toc_0">Shell echo命令</h2>

<h3 id="toc_1">打印字符</h3>

<pre><code class="language-text">// 下面两行代码效果一致
echo &quot;It is a test&quot;
echo It is a test
</code></pre>

<h3 id="toc_2">打印转义字符</h3>

<pre><code class="language-text">echo &quot;\&quot;It is a test\&quot;&quot;
// 引号也可以省略
echo \&quot;It is a test\&quot;
</code></pre>

<p>打印结果：</p>

<pre><code class="language-text">&quot;It is a test&quot;

&quot;It is a test&quot;
</code></pre>


                        
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                   <a href="15224936933861.html">Read more</a>&nbsp;&nbsp; 
                    <span class="date">2018/3/31</span>
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                  <h1>每天学习一个shell技能（4）</h1>
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                        	<h2 id="toc_0">shell基本运算符</h2>

<p>基本使用：</p>

<pre><code class="language-text">#!/bin/bash

val=`expr 2 + 2`
echo &quot;两数之和为 : $val&quot;
</code></pre>

<ul>
<li>表达式和运算符之间要有空格，例如 2+2 是不对的，必须写成 2 + 2，这与我们熟悉的大多数编程语言不一样</li>
<li>完整的表达式要被 ` ` 包含，注意这个字符不是常用的单引号，在 Esc 键下边</li>
</ul>


                        
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                  <h1>每天学习一个shell技能  (3)</h1>
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                        	<h2 id="toc_0">shell参数传递</h2>

<p>我们可以在脚本执行时，向脚本传递参数</p>

<pre><code class="language-text">// 终端运行 脚本，并传入参数
sh testBash.sh 0 1 2

echo &quot;Shell 传递参数实例！&quot;

echo &quot;\$0 =&gt; $0&quot;

echo &quot;\$1 =&gt; $1&quot;
</code></pre>

<p>打印结果：</p>

<pre><code class="language-text">Shell 传递参数实例！
$0 =&gt; testBash.sh
$1 =&gt; 0
</code></pre>


                        
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                   <a href="15223750607281.html">Read more</a>&nbsp;&nbsp; 
                    <span class="date">2018/3/30</span>
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                  <h1>每天学习一个shell技能 （1）</h1>
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                        	<h2 id="toc_0">准备</h2>

<p>bash 环境位置</p>

<pre><code class="language-text">#!/bin/bash
</code></pre>

<p><code>#!</code> 一个约定的标记，它告诉系统这个脚本需要什么解释器来执行，即使用哪一种 Shell</p>


                        
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                  <h1>每天学习一个shell 技能 （2）</h1>
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                        	<h2 id="toc_0">Shell 数组</h2>

<h3 id="toc_1">定义数组</h3>

<pre><code class="language-bash">array_name=(value1 value2 value3)

array_name2=(
value1
value2
value3
)

// 单独定义某个分量的值
array_name(0)=value0
</code></pre>


                        
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